Intrinsic excitation-dependent room-temperature internal quantum efficiency of AlGaN nanowires with varying Al contents

Aluminum gallium nitride (AlGaN) nanowires have become an emerging approach for semiconductor deep ultraviolet light-emitting devices. To further improve the device performance, it is critical to understand the optical quality of AlGaN nanowires. However, today, the room-temperature internal quantum efficiency (IQE) of AlGaN nanowires is predominantly analyzed by the temperature-dependent photoluminescence (PL) approach under one excitation power or taking the PL intensity ratio at the room temperature and low temperature with different excitation powers. In both cases, one needs to assume the low temperature IQE to be 100%, which is not always valid, in particular when the excitation power changes at the low temperature. In this work, we study the room-temperature IQE of AlGaN nanowires through the detailed excitation power-dependent PL experiments and theoretical analysis. This allows us to derive the intrinsic room-temperature IQE of AlGaN nanowires as a function of the excitation power. It is found that for an Al content in the range of 22%–54%, the IQE of all samples increases as the excitation increases, followed by an efficiency droop. Moreover, comparing different samples, the IQE at low excitations increases as the Al content increases, whereas the peak IQE reduces from 73% to 56% as the Al content increases. The underlying mechanisms are also discussed in this paper.